The present invention relates to poly (metal carboxylate) grafted rubbers having high modulus properties in the cured state. More particularly, the invention relates to a graft copolymer rubber comprising an unsaturated hydrocarbon rubber backbone having pendently grafted thereto a polymerized metal salt of an unsaturated carboxylic acid and to a method for preparing the graft copolymer rubber.
Rubber compounds having high modulus properties in the cured state are known in the art. Such rubber compounds have previously been prepared by mixing rubbers such as natural rubber, diene rubber, styrene/butadiene rubber, EPDM rubber and the like with a metal salt of an unsaturated carboxylic acid such as zinc dimethacrylate and an organic peroxide curing agent. Rubber compounds of this type are illustrated by U.S. Pat. Nos. 4,500,466 to Hayes et al; 4,529,770 to Hayes et al and 4,720,526 to Roland.
Rubber compounds of the type described in the above patents provide significant advantages in physical properties particularly increased strength in the cured state. However, such rubber compounds suffer from significant disadvantages due to the use of the metal salt as a separately added pigment and the use of peroxide curing agents. Thus, the mixing of such rubber compounds is often accompanied by undesirable odor problems, cure contamination, sensitivity of peroxides to heat and sticking of the metal salt to the mixing equipment.
Accordingly, the development of rubbers and rubber compounds which do not suffer from such disadvantages is a highly desirable objective. The present invention overcomes these disadvantages.